2. OPERATION LOGIC
Group | Status | Comment | |
4.0 | - 4.15 |
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5.0 |
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The DBF units are supplied with the following target LED’s default configuration:
LED | LEFT COLUMN | LED | RIGHT COLUMN |
1 | TRIP STAGE 1 | 9 | LOW SET PICKUP |
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2 | TRIP STAGE 2 | 10 | 50BF POLE A INIT |
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3 | PHASE A TRIP | 11 | 50BF POLE B INIT |
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4 | PHASE B TRIP | 12 | 50BF POLE C INIT |
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5 | PHASE C TRIP | 13 | INT. ARC A POLE |
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6 | 3P TRIP NO I | 14 | INT. ARC B POLE |
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7 | INT. ARC TRIP | 15 | INT. ARC C POLE |
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8 | HIGH SET PICKUP | 16 | REMOTE COMMUNICATIONS |
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2.2.4 CIRCUIT BREAKER BREAKING CAPACITY MONITORING
To supervise the breaker health, the DBF system calculates and stores, for each operation, the accumulated values of the square of the current multiplied by the opening time of the breaker (I2t) on each phase. I2t is expressed in kA2 sec.
The value I2t is accumulated and stored independently for each phase. These values can be accessed either by the local HMI or by the
The function has an Integration Time Selector setting (kI2t OP MODE) which can be used to assign a fixed opening time (given by another setting (kI2t INT TIME)). Otherwise the unit measures the time between the tripping signal of the main feeder protection and the change of the status contacts of the circuit breaker (52/b).
The total Breaking Current Limit (kI2t LIMIT) setting fixes the maximum life breaking capability (it is recommended to set this to the limit supplied by the manufacturer). When this threshold is reached in any phase, the system may be configured to close an output, if the appropriate internal signal (52 A Maintenance Alarm, 52 B Maintenance Alarm, 52 C Maintenance Alarm) is assigned to an output. In addition, the system also has a counter for the tripping operations.
The purpose of these functions is to provide accurate data to perform the circuit breaker maintenance, based on
the actual breaking time and current values. Once this maintenance operation has been done, the values for both
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the I t and number of opening operations, can be reset.
In order to be able to take into account the history of the breaker, in the case where the breakers were already in
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use before the installation of the relay, the system allows to set an initial value for the I t and the number of the previous breaking operations. Similarly, these values can be adjusted to a given value in order to take into account operations carried out during protection testing.
DBF Breaker Failure Protection | 9 |